BEIJING, Dec. 2 -- The first U.N. investigator granted access to China's vast network of prisons and labor camps said Friday he had documented widespread use of torture despite government efforts to obstruct his probe. He added that abuse of prisoners appeared to be declining.

Manfred Nowak, the U.N. special rapporteur on torture, said Chinese officials had informed him that the nation's highest court would begin handling all new death penalty appeals starting Jan. 1. That long-promised reform is expected to sharply reduce the use of capital punishment in a country that executes more prisoners every year than the rest of the world combined.

But Nowak said the Chinese government would have to overhaul its criminal laws, grant judges and defense attorneys greater powers and abolish efforts to "re-educate" inmates before it can eliminate torture in its prisons and meet international standards.

"The use of torture, though on the decline, particularly in urban areas, nevertheless remains widespread in China," he said at a news conference after a 13-day investigation involving unscheduled visits to nine detention facilities. "There is a need for much more structural reform."

Nowak said detainees he interviewed described being subjected to electric shocks and beatings by police officers under pressure to extract confessions, and to a range of punishments that leave no physical bruises and thus may not be illegal under Chinese law. The methods included sleep deprivation and being forced to stand, sit or squat in uncomfortable positions for hours and sometimes days at a time, Nowak said.

His conclusions were likely to upset the Chinese government, which agreed to the probe after a decade of lobbying by the U.N. Commission on Human Rights and by the United States and other foreign governments.

China had repeatedly rejected the U.N. demands for unannounced visits to detention centers and private meetings with detainees, standard conditions for the torture investigations the body conducts. But the government relented last December as part of a broader effort to work more closely with the United Nations and address international criticism of its human rights record.

Nowak said the government complied "in principle" with its promise to allow him to meet privately with any detainee in any detention facility in the country, a remarkable development given that China's secretive and powerful security ministries had long resisted outside scrutiny of the prisons and labor camps they manage.

But Nowak complained that police and state security officers obstructed his efforts to meet with former prisoners, family members, lawyers and human rights activists who were not in prison. He said that people across the country trying to meet him were detained and that undercover agents often followed, photographed and eavesdropped on him when he tried to meet with others.

"I was promised freedom of movement and inquiry, but there was serious interference," he said, describing the harassment as a violation of the agreement he reached with the Chinese. But he expressed satisfaction with his access to prisoners and the facilities he chose in Beijing, Tibet and Urumqi, the capital of Xinjiang province, home to the restive Muslim Uighur population that has been the target of a prolonged crackdown against ethnic separatism.

Nowak said, however, that he encountered "a palpable level of fear and self-censorship" worse than anything he had seen in more than two decades of similar experience.

Of the 30 or so detainees he interviewed, Nowak said in an interview, about half agreed to speak only after requesting absolute confidentiality. He said that others refused to answer questions or said they had forgotten the details of how they had been treated, and that some appeared "just brainwashed." He recalled one prison cell with 11 inmates who were afraid even to look up at him.

Among those who did agree to speak on the record was He Depu, a democracy activist who described being forced to lie still on his back in a cold room with his hands extended in front of him for 85 days. Another was Yang Jianli, the Boston-based dissident whose imprisonment has been protested by Congress and who described being subjected to electric shocks and beatings before he eventually suffered a stroke.

Nowak voiced particularly strong objections to the government's policy of trying to "re-educate" inmates, in its terminology, including those who have not been convicted of any crime, with political classes, forced labor and torture.

"It is an attempt to change the personality of an individual," he said, "and it is degrading treatment that strikes at the core of individual dignity and humanity."